russell@unturf.com
0a580b313d
Authors: russell@unturf.com · brackishbert@gmail.com · foxhop.net · TimeHexOn.com Patches, unit tests, benchmarks, whitepaper, and outreach briefs. Public domain — no copyright claimed. Use freely.
83 lines
2.7 KiB
Java
83 lines
2.7 KiB
Java
/*
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* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/* @test
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* @summary Test of a demo of an imperative stable value based on a lazy constant
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* @enablePreview
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* @run junit DemoImperativeTest
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*/
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import org.junit.jupiter.api.Test;
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import java.util.concurrent.atomic.AtomicReference;
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import static org.junit.jupiter.api.Assertions.*;
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final class DemoImperativeTest {
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interface ImperativeStableValue<T> {
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T orElse(T other);
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boolean isSet();
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boolean trySet(T t);
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T get();
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static <T> ImperativeStableValue<T> of() {
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var scratch = new AtomicReference<T>();
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return new Impl<>(scratch, LazyConstant.of(scratch::get));
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}
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}
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private record Impl<T>(AtomicReference<T> scratch,
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LazyConstant<T> underlying) implements ImperativeStableValue<T> {
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@Override
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public boolean trySet(T t) {
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final boolean result = scratch.compareAndSet(null, t);
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if (result) {
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// Actually set the value
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get();
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}
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return result;
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}
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@Override public T orElse(T other) { return underlying.orElse(other); }
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@Override public boolean isSet() { return underlying.isInitialized(); }
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@Override public T get() { return underlying.get(); }
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}
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@Test
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void basic() {
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var stableValue = ImperativeStableValue.<Integer>of();
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assertFalse(stableValue.isSet());
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assertEquals(13, stableValue.orElse(13));
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assertTrue(stableValue.trySet(42));
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assertFalse(stableValue.trySet(13));
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assertTrue(stableValue.isSet());
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assertEquals(42, stableValue.get());
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assertEquals(42, stableValue.orElse(13));
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}
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}
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